Presently, vaccination is the most important route of dealing with viral infections. Although a number of antiviral agents are available, typically, these agents have limited efficacy. Administering antibodies against a virus may be a good way of dealing with viral infections once an individual is infected (passive immunization). Typically, human or humanized antibodies hold promise for dealing with a number of viral infections, but the most efficacious and safe way of dealing with virus infection presently is, and probably will be, prophylaxis through active immunizations. Active immunization is generally referred to as “vaccination.” Vaccines comprise at least one antigenic determinant (typically of a virus), preferably a number of different antigenic determinants of at least one virus or other pathogen, for instance, by incorporating in the vaccine at least one (viral) polypeptide or protein derived from a virus (subunit vaccines).
Typically, vaccines include adjuvants in order to enhance the immune response. Use of adjuvants is also possible for vaccines that use whole virus (pathogen), for instance, when the virus is inactivated. Another possibility is the use of live, but attenuated, virus. A further possibility is the use of wild-type (“wt”) virus, for instance, in cases where adult individuals are not in danger of infection but infants are and may be protected through maternal antibodies and the like.
Producing vaccines is not always an easy procedure. In some cases, the production of viral material is on eggs, which may lead to materials that are difficult to purify and require extensive safety measures against, for instance, contamination. Likewise, production on bacteria or yeast, which is sometimes an alternative for eggs, can require many purification and safety steps.
Production on mammalian cells would be an alternative, but the mammalian cells used thus far have required, for instance, the presence of serum and/or adherence to a solid support for growth. In the first case, again purification and safety and, for example, the requirement of protease to support the replication of some viruses, becomes an issue. In the second case, high yields and ease of production become a further issue. The present invention overcomes at least a number of the problems encountered with the production systems for production of viruses and/or viral proteins for vaccine purposes of the systems of the prior art.